With my son and daughter-in-law both Iowa grads, I learned that "Natty Light" is the popular beer in campus. I used to roll my eyes at that, but just realized that it actually fits with the team nickname. "Hawkeye" comes from Hawthorne's Leatherstocking tales (Last of the Mohicans, etc.): Hawkeye being the nickname of the hero. As all U of I grads of course know, the character's actual name is NATTY Bumppo. So, if you run into any Hawkeye fans drinking a Natty light, be sure to compliment them on their literature-inspired joke.
If they give you a confused look, just point to the beer, mention Natty Bumppo, and laugh. I'm sure they'll figure it out then.